should we choose async await over Promise in Javascript

Question

I know that the async await is the new Promise in the town and it is a new way to write asynchronous code and I also know that

We didn’t ha

Answer 1

As most things go, the answer is "it depends".

Before talking about performance, the more important aspect is the maintainability of the code, and limitation of async/await vs raw Promise.

async/await is a great way to execute asynchronous code sequentially, while Promise enables you to run asynchronous code concurrently.

async function foo() {
  const a = await backend.doSomething()
  const b = await backend.doAnotherThing()
  return a + b
}

In the code above, backend.doAnotherThing() will not be executed until backend.doSomething() has returned. On the other hand:

function foo() {
  Promise.all([backend.doSomething(), backend.doAnotherThing()])
    .then(([a, b]) => {
       return a + b
    })
}

will execute both calls, and wait for both to complete.

As you mentioned about the benefits of async/await, I personally use it extensively. Except for the cases above.

If you need performance and to you, the performance difference between async/await vs Promise is more important than the readability benefit of async/await over Promise, by all mean go ahead.

As long as it is a conscious choice, you should be fine.

UPDATE: as mentioned by Derek 朕會功夫

You can get parallel execution with async/await by:

async function foo() {
  const p1 = backend.doSomething()
  const p2 = backend.doAnotherThing()
  return await p1 + await p2
}